Multi-component electronic packages and system-in-package (SIP) packages that are employed in the electronics industry today all utilize substrates for device inter-connection and attachment. Typical organic substrate materials are epoxy-glass, polyimide, and fluoropolymer laminates. Typical inorganic substrate materials are ceramics, low-temperature co-fire ceramics (LTCC) and silicon. The interconnect circuitry and component attach features are fabricated onto the substrates prior to components assembly.
With the exception of a silicon substrate, which employs thin-film metal deposition processes for the circuitry fabrication to yield line geometries on the order of one micrometer, all of the other substrate materials yield line geometries that are 50 micrometers or larger. A silicon substrate can only be used in single-sided applications and is often fragile in the final package form. The larger line geometries of the other substrates necessitate a larger final package size. The resultant longer interconnect lengths can also compromise package performance. Package designs with smaller package footprints and lower profiles, along with higher performance and yields, are ever being sought in the electronics industry.